HTI vaccine induces robust memory T cell responses in rhesus macaques. (A) Vaccination schedule. Four macaques (R678, R679, R680, R681) were vaccinated 3x (0, 1, 3 months) with DNA.HTI and IL-12 DNA and subsequently with two MVA.HTI boosts. Cellular immune responses were measured by intracellular cytokine staining after the different vaccinations as indicated. (B) The frequency of HTI-specific IFN-γ+ T cells was measured after the DNA vaccinations using peptide pools covering the complete HTI sequence. The HTI-specific CD4+ (open bars) and CD8+ (filled bars) T cells are shown for each animal as number of reactive peptide pools. (C) The frequencies of HTI-specific IFN-γ+ T cells with central memory (CM; CD28+CD95+) and effector memory (EM; CD28−CD95+) phenotype are shown over the course of the study.